This paper studies a new concept of using GNSS signals coherently reflected over relatively smooth ocean and ice surfaces from very low elevation angles (below ~8°) and received by low Earth orbit (LEO) satellites to retrieve the tropospheric information. This approach can provide horizontal profiles of tropospheric zenith delay and total column water vapor (TCWV) with centimeter-level high precision and spatial resolutions of 10s of km by ~1km, depending on the elevation angle, with a sampling spacing of ~100m. This approach can potentially be applied to most sea ice and calm ocean areas and provide tropospheric sensing data, which can complement and augment existing observation systems. A few case studies are conducted in this paper using the Spire grazing-angle GNSS-R data. The retrieved TCWV is compared to ERA5 products and the Sentinal-3 OLCI measurements and shows promising performances. The errors associated with the GNSS-R tropospheric measurements are also discussed.